Ensuring an adequate supply of clean water is an urgent global issue. The demand for clean water will continue to increase due to industrialization and population growth. Thus, the development of technologies that can effectively purify contaminated water has been an emerging area of research.
Adsorption-based technologies have been used to remove a variety of toxic chemicals from contaminated water via batch or continuous flow processes. The carboxyl and amine groups of activated carbon and polysaccharides such as alginate and chitosan are the most widely implemented adsorbents due to their ability to chelate toxic heavy metals. However, several limitations of existing absorbents can be identified.
First, the attachment of polysaccharides onto solid phases is essential, yet these adsorbents lack inherent adhesive properties to facilitate their immobilization onto substrates. As a result, complex multi-step chemical modifications of polysaccharides are required for surface immobilization, and implementing these methods on a wide variety of substrate surfaces is challenging.
Second, the generation of secondary pollutants during chemical processing of adsorbents is a serious environmental issue. In the case of activated carbon adsorbent, a strongly acidic solution (typically 10-50% (v/v) HNO3) has been used, whereas a variety of toxic chemicals and solvents have been used for chemical modification of the polysaccharide adsorbents.
Third, the variety of toxic chemicals that can be removed by existing adsorbents is limited. They often show excellent performance in the removal of heavy metals, but perform poorly in the removal of toxic organic molecules, particularly in the case of polysaccharide adsorbents.
Fourth, methods for regenerating adsorbents and isolating adsorbed toxic chemical complexes have not been adequately developed.
Finally, the cost of carbon materials is rapidly increasing, a particular concern for developing regions and resource-poor settings.
Thus, novel approaches to overcome the aforementioned limitations, in whole or in part, are needed for improved and more cost-effective water detoxification.